Filament-reinforced resin motor cases have been extensively used in the propulsion industry. Several advantages have resulted from employment of filament-reinforced resin motor cases. Some of the advantages include: light weight motor case, less insulation requirements for the filament-reinforced resin motor case, the ease of manufacture, storage, transportation, and stability against sparking or electrical conductance malfunctions.
Advanced interceptor motor case technology has placed additional requirements on the propulsion industry to ensure that these motor cases withstand the stresses due to high acceleration forces resulting from employing ultrahigh burning rate propellants and control systems which achieve high maneuverability to execute difficult tactical movements. It is well established that the strength of a motor case is weakened at points of stresses due to material weaknesses or fabrication techniques. For filament-reinforced composite motor cases, particularly, those that include a curable resin which undergo shrinkage on polymerization, stress due to shrinkage of the resin causes an inherent defect from the manufacture of the motor case.
An object of this invention is to provide a method of modifying the resin components which go into the manufacture of filament-reinforced composite motor cases wherein an elimination or reduction of shrinkage occurs during polymerization (or cure).
A further object of this invention is to provide a modification to the resin components which go into the manufacture of filament-reinforced composite motor cases wherein a bisspiroortho carbonate is incorporated into the epoxy resin blend to achieve an expansion during polymerization (or cure) of the modified epoxy resin blend to thereby prevent shrinkage and the stress due to the shrinkage normally encountered within the incorporated bisspiroortho carbonate which imparts an expansion during polymerization (or cure) of the modified epoxy resin blend.